A typical vane-type camshaft phaser generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to one of the advance and retard chambers and vacated from the other of the advance and retard chambers in order to rotate the rotor within the stator and thereby change the phase relationship between an engine camshaft and an engine crankshaft. Camshaft phasers also commonly include an intermediate lock pin which selectively prevents relative rotation between the rotor and the stator at an angular position that is intermediate of a full advance and a full retard position. The intermediate lock pin is engaged and disengaged by vented oil from the intermediate lock pin and supplying pressurized oil to the intermediate lock pin respectively.
Some camshaft phasers utilize one or more oil control valves located in the internal combustion engine to control the flow of pressurized oil to and from the advance chambers, retard chambers, and lock pin. One example of such a camshaft phaser is shown in U.S. patent application Publication No. 2010/0288215. In this arrangement, three separate supply signals need to be included in the camshaft bearing for communication to the camshaft phaser. More specifically, a first passage for the advance chambers, a second passage for the retard chambers, and a third passage for the lock pin is included in the camshaft bearing. Including three separate passages in the camshaft bearing undesirably increases the length of the camshaft bearing. Additionally, space may be limited in the internal combustion engine to package oil control valves therein which are needed to control oil to and from each of the three passages.
In order to eliminate the packaging concerns and increased camshaft bearing length issues associated with packaging the oil control valve in the internal combustion engine, some manufacturers have included the oil control valve coaxially within the camshaft phaser. While this arrangement is common for oil control valves that need to supply oil to the advance and retard chambers, the arrangement is less common for oil control valves that need to supply oil not only to the advance and retard chambers, but the intermediate lock pin as well. One example of such a camshaft phaser is shown in U.S. patent application Publication No. 2004/0055550. However, including a single oil control valve coaxially within the camshaft phaser to control oil to the lock pin in addition to the advance and retard chambers requires an increased camshaft phaser thickness in order to accommodate the passage supplying oil to and from the lock pin. A single oil control valve also prevents independent control of the lock pin function and the phasing function which may make engaging the intermediate lock pin with its lock pin seat difficult.
What is needed is an axially compact camshaft phaser with valving located coaxially within the camshaft phaser for controlling the phase relationship and for controlling the lock pin. What is also needed is such a camshaft phaser which allows for control of the phase relationship independent of the lock pin.